1. Field of the Invention
The present invention relates to an occupant protective apparatus which is used in a car to enhance the collision safety of the car.
2. Description of the Related Art
Recently, there has been proposed various car body structures in which, in order to enhance the protective effect of an occupant in a car collision, the deforming mode of the other remaining portions of a car body other than a car room portion of the car body in the car collision is set properly to thereby be able not only to reduce the deceleration of the car room portion of the car body but also to prevent the deformation of the other remaining portions of the car body from extending over the car room portion of the car body (see, for example, JP-A-7-101354).
On the other hand, a factor which influences the severity of injury to the occupant in a car collision, generally, is the maximum acceleration (or deceleration) of the occupant. Therefore, to reduce injury to the occupant in the car collision, first, the deceleration of the occupant (in the case of the forward collision of the car) should be reduced. Deceleration of the occupant is caused by a force which is applied to the occupant from a restricting device such as a seat belt. Generally, the seat belt functions as a spring. That is, when the occupant is moved forward due to the inertial force thereof, and the extension of the seat belt reaches its limit, the occupant deceleration reaches its peak value. The peak value of the occupant deceleration increases the more the occupant is displaced due to the inertial force. Such peak value is generally higher than the average deceleration of the car body.
In a case where the relation between the car body deceleration and occupant deceleration is assumed to be input and output with respect to a system composed of the spring (restricting device) and mass (the mass of the occupant), the maximum extension of the spring and the time of such extension can be derived from a waveform (variations in deceleration with the passage of time) that represents the deceleration of the car body. Therefore, in order to reduce the occupant deceleration in a car collision, the waveform of the car body deceleration must be adjusted in such a manner that not only the average deceleration of the car body can be reduced but also the overshoot of the spring can be minimized as much as possible.
In a conventional car body structure, a crashable zone, which is constructed between a collision reaction force generating member (such as a side beam) and the respective components of the car body structure, is disposed in the front portion of the car body. In a car collision, the crashable zone is deformed to thereby absorb collision energy caused by the car collision. As such, selectively setting the dimensions of the respective car body components so as to change characteristics of the collision reaction force, adjusts the waveform of the car body deceleration.
As described above, the waveform of the car body deceleration is an important factor in reducing the occupant""s injuries. The waveform representing the deceleration of the body of a car at time of collision is illustrated in FIG. 9, by a solid line. The deceleration of the car body can reduce the occupant deceleration to the above-mentioned occupant damage reduction level. As shown in FIG. 9, a larger deceleration than an average deceleration is generated for a given short period of time in the initial stage of a car collision. Continuously with this, deceleration going in the opposite direction is then generated for a given period of time (a short period of time). Thereafter, the car body decelerates with average deceleration. A simulation conducted by the present inventors has confirmed that, according to such car body deceleration waveform, the occupant deceleration can be made smaller than in a constantly decelerating waveform (a rectangular waveform) where a distance (a dynamic stroke) necessary for deceleration of the car body is kept constant.
In a conventional car body structure, at the initial stage of collision, the crashable zone is always deformed so that the relatively low-strength portion of the crashable zone is deformed first and the high-strength portion thereof is deformed second. The collision reaction force, namely, the car body deceleration shows a waveform in which the car body deceleration is small in the initial stage of the collision and increases in the late stage of the car collision. That is, it cannot be said that the conventional car body structure is sufficiently effective on reduction of the occupant deceleration.
Also, conventionally, there are proposed a method for making use of crashing of the side beam to thereby obtain a constant reaction force, and a method for providing a plurality of separation walls respectively at a plurality of positions of the side beam to thereby obtain a stable reaction force (JP-A-7-101345).
However, these conventional methods truly allow the car body deceleration to approach a constant deceleration (a rectangular waveform). But it is quite difficult to obtain a more effective deceleration waveform, such as the waveform shown in FIG. 9.
Also, in an electric car, there is proposed a structure in which a battery box carried on the central portion of the car body is supported in a movable manner to reduce the mass of the car body that receives a load generated by the side beam in the initial stage of a car collision and improve a deceleration waveform of the car body (see JP-A-5-238287, JP-A-5-246252, JP-A-5-246253).
However, the above-mentioned structure is limited to an electric car with a battery box carried on the central portion of the car body. Also, the mass of a battery is small for the whole car body. A problem with this structure is that the effect thereof on the improvement in the deceleration waveform is limited.
In order to reduce the deceleration of the occupant over the above-mentioned conventional occupant protective apparatus, it is necessary to generate such a car body deceleration waveform as shown in FIG. 9.
The present invention aims at eliminating the drawbacks found in the above-mentioned conventional occupant protective apparatus. Accordingly, it is an object of the invention to provide a car occupant protective apparatus which, using a simple structure, not only properly reduces the deceleration of an occupant in a car collision, but also reduces the size of a car body.
In attaining the above object, according to the invention, an occupant protective apparatus for use in a car, comprises: a movable part 2 formed integral with the base of an occupant seat 8 (or seat 8 itself) such that when the car is in a collision, the movable part 2 moves back and forth with respect to the body of the car. An occupant restricting unit (seat belt 9) is disposed on the occupant seat 8 or on the movable part 2 for restricting an occupant seated on the occupant seat 8.
An impact absorbing part (side beam 3), absorbs collision energy generated in the car body with certain deceleration. A first load transmission member (transmission rod 6 or front side portion of the side frame 13), in the initial stage of the car collision, moves the movable part 2 backward due to transmission of a collision load caused by the car collision. A weight member (engine 11) is supported on the rear portion of the car body in such a manner that it can be moved forward with respect to the car body.
Some embodiments further comprise a second load transmission member 12 (or the rear side portion of the side frame 13), for transmitting a forward load of the weight member (engine 11) to the movable part 2, wherein, in case of a car collision, the collision load is transmitted to the movable part 2 by the first load transmission member to move the movable part backward by a given amount with respect to the car body to thereby apply high deceleration to the movable part 2 temporarily.
Thereafter, the forward load of the weight member (engine 11) moves forward due to the inertia thereof and is transmitted to the movable part 2 by the second load transmission member 12 to thereby apply a forward acceleration to the movable part 2 temporarily. As such, the collision energy is absorbed by the whole car body.
According to above-structured occupant protective apparatus, in the car collision, a load caused by the car collision is transmitted to the movable part 2 by the first load transmission member (transmission rod 6), thereby generating larger deceleration than average deceleration in the movable part 2 for a given period of time (for a short period of time); next, the forward load of the weight member (engine 11) is applied to the movable part 2 to thereby generate opposite deceleration (acceleration) in the movable part 2 for a given period of time (for a short period of time). Thereafter, the collision energy is absorbed by the impact absorbing part (side beam 3) so that the occupant""s deceleration reaches an average deceleration little by little. Accordingly, the deceleration of the occupant is prevented from increasing suddenly. FIG. 9 illustrates a waveform representing the deceleration of an occupant at the time of collision, in accordance with one or more embodiments.
Also, according to another aspect of the invention, there is further included a shock absorbing structure (the second load transmission member 12 also functions as this structure) which is interposed between the car body and the weight member (engine 11). Accordingly, deceleration to be generated after generation of the forwardly going acceleration can be prevented from increasing suddenly.
The above-mentioned weight member may be an engine, a transmission, various kinds of motors, a battery, or other structure.